This invention relates to a fuel injection system and more particularly to an improved fuel injection system for two cycle engines.
The advantages of two cycle engines are well known. Their simplicity and the relatively high power output per crankshaft revolution makes these engines very desirable. However, one disadvantage of previously proposed two cycle engines is the somewhat poor fuel economy and high emission under certain conditions due to the porting of the engine. It has been proposed to improve the efficiency of a two cycle engine by incorporating direct cylinder injection. Either fuel injectors or air/fuel injectors have been proposed for this purpose.
Although direct fuel injection permits an improvement in fuel economy and emission control for two cycle engines, it does present some problem. In a conventional two cycle engine, a mixture of fuel and air is delivered to the crankcase chamber of the engine and then transferred to the combustion chamber for combustion. Hence, the fuel/air mixture is present both on the underside and on the head side of the piston and effective cooling is achieved under all running conditions. However, when direct fuel injection is employed, there is no cooling on the underside of the piston and direct injected engines must have their maximum power output limited to avoid problems due to this diminished cooling affect.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for a two cycle engine that will permit the operation of the engine under high speed and load conditions without adverse thermal effects.
It is a further object to this invention to provide an improved fuel injection system for a two cycle engine that incorporate direct cylinder injection but also incorporates another injection system for cooling the underside of the piston under high speed, high load conditions.
It has been proposed to solve the aforenoted problem through the incorporation of a sub injection system in addition to a main injection system with the sub or auxuliary injection system supplying fuel to the engine through its induction system under high speed running conditions. Although the supply of additional fuel through the induction system under this condition can permit operation at high speeds and loads, some problems can exist with the previously proposed system. That is, with these systems it is important to insure that the introduction of additional fuel by the sub injector does not cause an overrich mixture in the engine during each cycle which could result in poor fuel economy and poor emission control. Furthermore, the control of the amount of fuel discharged by the respective injectors must be accurately controlled so as to avoid the deleterious affects.
It is, therefore, a principal object to this invention to provide an improved injection system for an engine embodying main and auxiliary fuel injectors and in which the amount of fuel injected by these injectors is accurately controlled so as to provide the optimum fuel under all running conditions.
It is a further object to this invention to provide an improved fuel injection system for a two cycle engine that permits optimum fuel control and efficiency under all running conditions while insuring good cooling under high speed and high load conditions.
Another problem in conjunction with direct cylinder injection, particularly in two cycle engines, is that the conditions in the combustion chamber vary significantly as the load changes. In addition, cylinder to cylinder variations and pressure can become quite large in multiple cylinder two cycle engines and this can affect the cylinder to cylinder fuel/air mixture. Obviously, unbalances in the fuel/air charge in the individual cylinders can adversely affect engine performance.
It is, therefore, a still further object to this invention to provide an improved fuel injection system that will insure against cylinder to cylinder fuel/air variations under all running conditions.